1. Field of the Invention
The present invention relates to a communication apparatus, a portable terminal, and a communication control program which control ON/OFF of an execution apparatus, according to the result of communication therewith.
2. Related Background Art
Recently, what is called a keyless system has come into wide use which permits locking and unlocking a car door from a distance without the need for a physical key. A typical keyless system uses extremely weak radio waves of a frequency about 300 MHz or below to perform user authentication between the user's key and a radio authentication module installed in the car. When the use's key is authenticated, sends a locking or unlocking signal from the radio authentication module to the car. In such weak radio-wave base stations, no license is required for operation of a radio station; and radio waves of around 300 MHz well cover a range of about 10 m.
With the most popular keyless system in use, it is necessary for the user to press a button on the key when a user wants to open (close) the door lock. In this case, the user follows the procedure described below.
The user: (1) walks up to the car; (2) feels inside his or her pocket or bag for the key; (3) takes it out; and (4) presses the button on the key to undo the door lock (5).
The radio authentication module mounted in the car periodically tries to receive radio waves from the key. Accordingly, when the radio wave from the key actuated by user's pressing of the button on the key is received by the radio authentication module, authentication is immediately performed, which is followed by opening (closing) the door lock. When the button on the key is not pressed, no radio waves are not sent from the key—this lengthens the lifetime of the battery (2 to 5 years under normal usage condition) built in the key.
To solve another problem of the locking/unlocking system by radio waves, for example, to prevent faulty or erroneous unlocking, there is proposed a system that automatically closes the door lock a certain elapsed time after opening the lock. In this case, although the door is opened to get on the vehicle, the door is automatically closed when it takes much time to load baggage, thereby imposing inconvenience on the user. There is also known an invention intended as a solution to this problem (See Japanese Patent Application Laid-open No. 2001-115707).
The actuation of the button on the key will be described below. The button actuation is necessary for suppressing the power consumption of the key battery to length the battery life. But the actuation of the button impairs user convenience. That is, to open the door lock when the user has an umbrella or other stuffs in hand on the same side as the pocket in which the key is carried, or when the user carries his belongings in both hands, it is necessary for the user to shift the umbrella or the other stuffs from one hand to the other or place them somewhere around the user.
To improve user's convenience, there are also proposed keyless systems that do not involve the button actuation. In conventional keyless systems, to open the door lock when the user has an umbrella or other stuffs in hand on the same side as the pocket in which the key is carried, or when the user carries his belongings in both hands, it is necessary for the user to shift the umbrella or the other stuffs from one hand to the other or place them somewhere around the user. On the contrary, these keyless systems without involving the button actuation obviate the inconveniences arising from the actuation of the button even when the user has belongings in both hands.
The keyless systems roughly have two types. The one type is that uses extremely weak radio waves as in the above, and the key enters a radio wave sending mode and a radio wave receiving mode at regular time intervals. When the user carrying the key approaches the car and each of the key and the car enters the radio wave coverage of the other, authentication is automatically performed based on authentication protocols to unlock the car door.
In the other type of keyless system, although the key similarly enters the radio wave sending and receiving modes at regular time intervals, the car normally stops its communication facility at all times, and when the user presses an instruction button mounted on the car door in proximity to the door handle, the car activates the communication facility. If the key stays within the radio wave coverage at that time, authentication is performed based on authentication protocols to open the door lock.
The authentication (encryption) algorithm for the authentication of the keyless systems is usually a common key system. For example, in the case where the system is built up using a cutting-edge encryption algorithm, such as AES, and a key of a sufficiently long key length, it is impossible with the computing power of the present-day computers to decrypt the key within an actual time to open the door lock. Accordingly, this system provides increased security as compared with ordinary systems using physical keys.
Furthermore, there has been developed a system which performs ignition of a car engine through authentication by an encryption algorithm with a view to utilizing the security of the key encryption algorithm. In an ignition key system generally called an immobilizer, when the user inserts the key into an ignition hole and turns it to a predetermined position, a current signal flows between the key hole and the key, and authentication is performed between an authentication module built in the key and the immobilizer directly connected to the engine based on authentication protocols.
As described above, the car key system has introduced therein a wide variety of techniques so as to improve user convenience and security. In the current car key systems, however, the user cannot open/close door lock and start the engine unless he carries the key device exclusive to the car. If the above-mentioned function of the key device is incorporated in some other device that the user carries in every day life, user convenience could be further improved.
One possible device that the user carries on a day-to-day basis is a portable terminal such as portable telephone or PDA. The portable telephone enables communications with a fixed telephone or other portable telephones and access to the Internet via radio base stations installed by portable telephone providers. In recent years, there is a move afoot to install a second wireless communication apparatus in the portable telephone. The second wireless communication apparatus has, in principle, a coverage area from close proximity to 100 m, and enables communications with other terminals without the radio base stations by the providers.
Attention is being given to the Bluetooth™ communication system that utilizes the ISM band of the 2.4 GHz band and its neighboring frequencies and is not required to obtain a license. Conventional radio LANs have an effective coverage area of 100 m or more, whereas the Bluetooth system has a smaller coverage area, and consumes less power accordingly. Hence, this system is suitable for use in an information processor whose battery life is limited, such as a portable telephone. In recent years, portable telephones using the Bluetooth communication system and PDA or similar portable information processors (hereinafter, simply “portable terminals”) are becoming widespread. As for the details of Bluetooth, its specification can be obtained on a Website http://www.bluetooth.org/.
If the Bluetooth and other wireless communication apparatuses could be applied to the keyless system to open/close the door lock and start ignition of the car engine, the user would not be required to carry the key dedicated for the car, thereby improving user convenience. However, since the wireless communication apparatus mounted in the portable terminal is intended mainly for information transmission at a high transfer rate, not merely for opening/closing the door lock and so on, the application of such a wireless communication apparatus to the keyless system poses such problems as mentioned below.
The first problem is power consumption. The wireless communication apparatus built in the portable terminal is designed for high-speed data transfer as mentioned above, and consumes much more power than low-speed, low-frequency radio modules used in the keyless systems. Accordingly, from the viewpoints of the power consumption of the portable terminal and the battery life, it is difficult to implement a system that automatically opens the door lock when the user approaches the car.
Another problem is the coverage area. Ordinary keyless systems are intended only to open/close the door lock and have an optimum coverage area of about 10 m, for instance, and hence such systems can be designed and mounted in the portable terminal. However, the wireless communication apparatus of the portable terminal is designed for data transfer. Further, since the coverage area is determined by the wireless communication specifications, it is difficult to set the coverage area optimum for the keyless system. In the case of the Bluetooth system, a Class 3 module is usually mounted in the portable terminal, but its effective coverage area is as large as approximately 20 m. Accordingly, even when the user passes by the car at some distance with no intension of approaching the car, authentication is likely to be performed, resulting the door lock being opened.